my mum brought a metal one off ebay, it can be used outside too (not sure how secure it would be outside though) she only uses it indoors as a play pen, its like the hammster ones you see but bigger so they can't escape.
If I'm really honest, I think the ball pit was a bit of a waste of time, I'm glad I only paid Â£9. It's way too small for my guys, so it's only suitable for a really quick twenty minutes whilst I clean out their C&C. Daisy, loving to nibble, has already made a hole in it big enough for an elephant to climb out, so I can't really use it again.....I had to get one of my daughters to watch them in it, so now one daughter has a lap full of Piggles and the other helps me clean out the enclosure! Anyone interested in a nibbled ELC ballpit?! X